Delivery apparatus for prosthetic heart valve

ABSTRACT

Embodiments of the present disclosure provide a delivery apparatus for a prosthetic heart valve. Disclosed delivery apparatuses can include a handle, a first shaft extending from the handle, a second shaft disposed around the first shaft, and a valve cover. The valve cover can be coupled to a distal end portion of the first shaft and can be configured to house a prosthetic heart valve in a radially compressed state. The valve cover can have an outer diameter greater than an outer diameter of the second shaft, and the first shaft and valve cover can be movable together in an axial direction relative to the second shaft.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/216,246, filed Dec. 11, 2018, which is a continuation of U.S. patentapplication Ser. No. 15/042,049, filed Feb. 11, 2016, which is acontinuation of U.S. patent application Ser. No. 14/066,259, filed Oct.29, 2013, which is a continuation of U.S. patent application Ser. No.11/852,977, filed Sep. 10, 2007, now U.S. Pat. No. 8,568,472, whichclaims the benefit of U.S. Patent Application No. 60/843,470, filed Sep.8, 2006, the entire disclosures of which are incorporated herein byreference.

FIELD

The present application concerns embodiments of a system for deliveringa prosthetic valve to a heart via the patient's vasculature.

BACKGROUND

Endovascular delivery catheters are used to implant prosthetic devices,such as a prosthetic valve, at locations inside the body that are notreadily accessible by surgery or where access without surgery isdesirable. The usefulness of delivery catheters is largely limited bythe ability of the catheter to successfully navigate through smallvessels and around tight bends in the vasculature, such as around theaortic arch.

Known delivery apparatuses include a balloon catheter having aninflatable balloon that mounts a prosthetic valve in a crimped state anda retractable cover that extends over the valve to protect the interiorwalls of the vasculature as the valve is advanced to the implantationsite. Various techniques have been employed to adjust the curvature of asection of the delivery apparatus to help “steer” the valve throughbends in the vasculature. The balloon catheter may also include atapered tip portion mounted distal to the balloon to facilitate trackingthrough the vasculature. The tip portion, however, increases the lengthof the relatively stiff, non-steerable section of the apparatus.Unfortunately, due to the relatively long stiff section, successfuldelivery of a prosthetic valve through tortuous vasculature, such asrequired for retrograde delivery of a prosthetic aortic heart valve, hasproven to be difficult.

A known technique for adjusting the curvature of a delivery apparatusemploys a pull wire having a distal end fixedly secured to the steerablesection and a proximal end operatively connected to a rotatableadjustment knob located outside the body. Rotation of the adjustmentapplies a pulling force on the pull wire, which in turn causes thesteerable section to bend. The rotation of the adjustment knob producesless than 1:1 movement of the pull wire; that is, rotation of the knobdoes not produce equal movement of the steerable section. To facilitatesteering, it would be desirable to provide an adjustment mechanism thatcan produce substantially 1:1 movement of the steerable section.

It is also known to use an introducer sheath for safely introducing adelivery apparatus into the patient's vasculature (e.g., the femoralartery). An introducer sheath has an elongated sleeve that is insertedinto the vasculature and a seal housing that contains one or moresealing valves that allow a delivery apparatus to be placed in fluidcommunication with the vasculature with minimal blood loss. Aconventional introducer sheath typically requires a tubular loader to beinserted through the seals in the sheath housing to provide anunobstructed path through the seal housing for a valve mounted on aballoon catheter. A conventional loader extends from the proximal end ofthe introducer sheath, and therefore decreases the available workinglength of the delivery apparatus that can be inserted through the sheathand into the body.

Accordingly, there remains a need in the art for improved endovascularsystems for implanting valves and other prosthetic devices.

SUMMARY

Certain embodiments of the present disclosure provide a heart valvedelivery apparatus for delivery of a prosthetic heart valve to a nativevalve site via the human vasculature. The delivery apparatus isparticularly suited for advancing a prosthetic valve through the aorta(i.e., in a retrograde approach) for replacing a stenotic native aorticvalve.

The delivery apparatus in particular embodiments includes a ballooncatheter having an inflatable balloon which mounts a crimped valve fordelivery through the patient's vasculature. The delivery apparatus caninclude a guide, or flex, catheter having a shaft that extends over theshaft of the balloon catheter. The guide catheter shaft has a steerablesection, the curvature of which can be adjusted by the operator tofacilitate navigation of the delivery apparatus around bends in thevasculature. The delivery apparatus also can include a nose catheterhaving a shaft that extends through the balloon catheter shaft and anose piece located distally of the valve. The nose piece desirably has atapered outer surface and is made of a flexible material to provideatraumatic tracking through the arteries and a stenotic native valve.The nose piece desirably has an internal bore that is dimensioned toreceive at least a distal end portion of the deflated balloon duringdelivery of the valve.

By inserting a portion of the balloon into the nose piece, the length ofthe non-steerable section of the delivery apparatus can be reduced(e.g., by about 1.5 to 2.0 cm in some examples), which greatly enhancesthe ability of the delivery apparatus to track through the aortic archwith little or no contact between the end of the delivery apparatus andthe inner walls of the aorta. Once the delivery apparatus has beenadvanced to the implantation site, the nose catheter can be moveddistally relative to the balloon catheter to withdraw the balloon fromthe nose piece so as not to interfere with inflating the balloon.

The guide catheter shaft can be provided with a cover at its distal endto cover a portion of the balloon and/or the valve that is not alreadycovered by the nose piece. In particular embodiments, the cover extendsover the remaining portion of the balloon and the valve that is notcovered by the nose piece. In this manner, the entire outer surface ofthe valve and the balloon are shielded by the nose piece and the cover.Consequently, an introducer sheath need not be used to introduce thedelivery apparatus into the patient's vasculature. Unlike an introducersheath, the cover need only be in contact with the femoral and iliacarteries for only a short period of time, and thus minimizes thepossibility of trauma to these vessels. Further, by eliminating theintroducer sheath, the maximum diameter of the system can be reduced,and therefore it is less occlusive to the femoral artery.

In one variation of the delivery apparatus, the nose piece has aninternal bore dimensioned to receive the entire valve and substantiallythe entire balloon during delivery of the valve. Thus, in thisembodiment, the cover attached to the end of the guide catheter need notbe provided. In another variation, the cover of the guide catheterextends completely over the valve and the balloon, and the nose catheteris not provided. The cover can be an expandable mesh basket that cancollapse around the valve and the balloon to provide a smooth trackingprofile. The mesh basket can be expanded by the operator, such as bypulling one or more pull wires, which dilates a distal opening in themesh basket permitting the balloon and the valve to be advanced from thebasket for deployment.

As noted above, the guide catheter desirably has a steerable sectionthat can be deflected or bent by the operator to assist in tracking thedelivery apparatus around bends in the vasculature. In certainembodiments, the guide catheter can be provided with a manually operatedadjustment mechanism that produces substantially 1:1 movement of thesteerable section. To such ends, the adjustment mechanism can include apivotable lever that is operatively coupled to the steerable section viaa pull wire extending through a lumen in the guide catheter shaft.Pivoting the lever operates a pulley, which retracts the pull wire,producing substantially 1:1 movement of the steerable section. Pivotingthe lever in the opposite direction releases tension in the pull wire,and the resiliency of the steerable section causes the steerable sectionto return to its normal, non-deflected shape.

In cases where an introducer sheath is used to assist in inserting thedelivery apparatus into the patient's vasculature, the introducer sheathcan be provided with an integrated loader tube that extends into theseal housing of the sheath. The loader tube is connected to an end piececoupled to the distal end of the seal housing. The end piece is moveablealong the length of the seal housing between a first, extended positionwhere the loader tube is spaced from the sealing valves in the sealhousing and a second, retracted position where the loader tube extendsthrough the sealing valves to provide an unobstructed pathway for avalve mounted on a balloon catheter. Because the loader tube does notextend behind the end piece, the loader tube does not decrease theavailable working length of the delivery apparatus that can be insertedthrough the sheath and into the vasculature.

In one representative embodiment, an apparatus for delivering aprosthetic valve through the vasculature of a patient comprises aballoon catheter, a guide catheter, and a nose catheter configured tomove longitudinally relative to each other. The balloon cathetercomprises an elongated shaft and a balloon connected to a distal endportion of the shaft, the balloon being adapted to carry the valve in acrimped state and being inflatable to deploy the valve at animplantation site in the patient's body. The guide catheter comprises anelongated shaft extending over the balloon catheter shaft, the shaft ofthe guide catheter comprising a steerable section. The guide catheterfurther comprises an adjustment mechanism operatively coupled to thesteerable section. The adjustment mechanism is configured to adjust thecurvature of the steerable section and the portion of the ballooncatheter shaft extending through the steerable section. The nosecatheter comprises an elongated shaft extending through the ballooncatheter shaft and a nose piece connected to a distal end of the nosecatheter shaft. The nose piece has an internal bore adapted to receiveat least a distal end portion of the balloon in a deflated state duringdelivery of the valve.

In another representative embodiment, a method of implanting aprosthetic valve at an implantation site in a patient's body comprisesplacing the valve on an inflatable balloon of a balloon catheter of adelivery apparatus and inserting at least a distal end portion of theballoon in a nose piece of a nose catheter of the delivery apparatus.The balloon catheter and the nose catheter are then inserted into thebody and advanced through the patient's vasculature. At or near theimplantation site, the nose catheter is moved distally relative to theballoon catheter to uncover the portion of the balloon inside the nosepiece, and thereafter the valve can be deployed at the implantation siteby inflating the balloon.

In another representative embodiment, a method of implanting aprosthetic valve at an implantation site in a patient's body comprisesplacing the valve in a crimped state on the distal end portion of anelongated delivery apparatus and advancing the delivery apparatusthrough the patient's vasculature. Subsequent to the act of advancingthe delivery apparatus, the crimped valve is moved onto an inflatableballoon on the distal end portion of the delivery apparatus and thendeployed at the implantation site by inflating the balloon.

In yet another representative embodiment, an apparatus for delivering aprosthetic valve through the vasculature of a patient comprises aballoon catheter and a nose catheter. The balloon catheter comprises anelongated shaft, a balloon connected to a distal end portion of theshaft, and a tapered wedge connected to the distal end portion adjacentthe balloon. The nose catheter comprises an elongated shaft extendingthrough the shaft of the balloon catheter, the balloon, and the wedge.The nose catheter further includes a nose piece connected to a distalend of the nose catheter shaft. The valve can be mounted in a crimpedstate between the nose piece and the wedge. The nose piece can beretracted proximally to push the valve over the wedge and onto theballoon, with the wedge partially expanding the valve before it isplaced on the balloon.

In another representative embodiment, a guide catheter for anendovascular delivery apparatus comprises an elongated shaft having asteerable section, a handle comprising a pivotable lever, and a pullwire. The pull wire has a proximal end portion coupled to the lever anda distal end portion fixedly secured to the steerable section such thatpivoting movement of the lever applies a pulling force on the pull wireto cause the steerable section to bend.

In another representative embodiment, an endovascular delivery apparatuscomprises a balloon catheter comprising an elongated shaft and a balloonconnected to a distal end portion of the shaft. A guide cathetercomprises an elongated shaft comprising an inner polymeric tubular linerhaving a lumen sized to permit insertion of the balloon and the ballooncatheter shaft therethrough. The shaft further comprises a braided metallayer surrounding the tubular liner, and an outer polymeric layersurrounding the braided metal layer.

In another representative embodiment, a method for making a cathetercomprises forming an inner tubular layer from a polymeric material, theinner tubular layer having a lumen dimensioned to allow a balloon of aballoon catheter to pass therethrough, forming a tubular pull wireconduit from a polymeric material, placing the conduit and the innertubular layer side-by-side in a parallel relationship relative to eachother, forming a braided metal layer around the conduit and the innertubular layer, and forming an outer polymeric layer around the braidedmetal layer.

In another representative embodiment, an introducer sheath comprises anelongated tubular sleeve having a lumen and adapted to be inserted intoa patient's vasculature, a seal housing comprising an inner bore incommunication with the lumen of the sleeve and one or more sealingvalves housed in the bore, and an end piece coupled to the sealinghousing opposite the sleeve. The end piece comprises a loader tubeextending into the bore and is moveable along a length of the sealhousing to move the loader tube from a first position spaced from theone or more sealing valves to a second position wherein the loader tubeextends through the sealing valves.

The foregoing and other features and advantages of the invention willbecome more apparent from the following detailed description, whichproceeds with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is side view of an endovascular delivery apparatus for implantinga prosthetic valve, according to one embodiment.

FIG. 2A is side view of the balloon catheter of the delivery apparatusof FIG. 1, shown partially in section.

FIG. 2B is an enlarged, cross-sectional view of the balloon cathetershown in FIG. 2A, taken along the length of the catheter.

FIG. 3A is a cross-sectional view of the guide catheter of the deliveryapparatus of FIG. 1, taken along a plane extending along the length ofthe guide catheter.

FIG. 3B is a cross-sectional view of the guide catheter, taken along aplane that is perpendicular to the plane defining the cross-section viewshown in FIG. 3A.

FIG. 4A is a cross-sectional view of the nose catheter of the deliveryapparatus shown in FIG. 1, taken along the length of the nose catheter.

FIG. 4B is an enlarged, cross-sectional view of the nose catheter.

FIGS. 5A and 5B are cross-sectional and perspective views, respectively,of a slide nut used in the handle portion of the guide catheter.

FIGS. 6A and 6B are perspective and side views, respectively, of aninner sleeve used in the handle portion of the guide catheter.

FIG. 7A is a cross-sectional view of a guide catheter, according to oneembodiment, taken along the length thereof.

FIG. 7B is a transverse cross-sectional view of the guide catheter shownin FIG. 7A.

FIG. 7C is an enlarged, longitudinal cross-sectional view of the distalend portion of the guide catheter shown in FIG. 7A.

FIGS. 8A-8C are cross-sectional views of the distal end portion of thedelivery apparatus of FIG. 1, illustrating the operation of the same forimplanting a prosthetic valve.

FIG. 9 is side view of an endovascular delivery apparatus for implantinga prosthetic valve, according to another embodiment.

FIG. 10A is a side view of the introducer sheath of the deliverapparatus shown in FIG. 9.

FIG. 10B is a side view of the introducer sheath of FIG. 10A shownpartially in section.

FIG. 10C is an end view of the introducer sheath of FIG. 10A.

FIG. 11 is a perspective view of an alternative embodiment of a guidecatheter.

FIG. 12 is a top plan view of the guide catheter of FIG. 11.

FIG. 13 is a side elevation view of the guide catheter of FIG. 11.

FIG. 14 is a perspective, exploded view of the guide catheter of FIG.11.

FIG. 15 is a partial, cross-sectional view of the guide catheter of FIG.11.

FIGS. 16A and 16B are perspective views of a pulley used in the guidecatheter of FIG. 11.

FIG. 17 is a perspective view of a lever portion used in the guidecatheter of FIG. 11.

FIGS. 18A and 18B are partial, cross-sectional views of the guidecatheter of FIG. 11 illustrating the operation of an adjustable leverfor adjusting the curvature of the guide catheter.

FIG. 19A is a perspective view of the distal end portion of alternativeembodiment of a nose catheter.

FIGS. 19B and 19C are cross-sectional views illustrating the operationof the nose catheter shown in FIG. 19A.

FIG. 20A is a side elevation view of the distal end portion of adelivery apparatus, according to another embodiment.

FIG. 20B is a transverse cross-sectional view of the guide catheter ofthe delivery apparatus of FIG. 20A.

FIGS. 21A-21C are cross-sectional views of an alternative embodiment ofa delivery apparatus, illustrating the operation of the same forimplanting a prosthetic valve.

FIGS. 22A and 22B are cross-sectional views of the distal end portion ofanother embodiment of a delivery apparatus.

FIG. 23A shows a cross-sectional view of another embodiment of anintroducer sheath and an exemplary delivery apparatus that can beintroduced into a patient's vasculature via the sheath.

FIG. 23B is a cross-sectional view of the introducer sheath of FIG. 23Aafter insertion of the delivery apparatus into the sheath.

FIGS. 24A-24B are cross-sectional views of another embodiment of adelivery apparatus.

FIGS. 25A-25E schematically illustrate another embodiment of a deliveryapparatus.

FIGS. 26A-26E schematically illustrate another embodiment of anintroducer sheath.

DETAILED DESCRIPTION

FIG. 1 shows a delivery apparatus 10 adapted to deliver a prostheticheart valve 12 (e.g., a prosthetic aortic valve) to a heart, accordingto one embodiment. The apparatus 10 generally includes a steerable guidecatheter 14 (also referred to as a flex catheter), a balloon catheter 16extending through the guide catheter 14, and a nose catheter 18extending through the balloon catheter 16. The guide catheter 14, theballoon catheter 16, and the nose catheter 18 in the illustratedembodiment are adapted to slide longitudinally relative to each other tofacilitate delivery and positioning of the valve 12 at an implantationsite in a patient's body, as described in detail below.

The guide catheter 14 includes a handle portion 20 and an elongatedguide tube, or shaft, 22 extending from the handle portion 20. Theballoon catheter 16 includes a proximal portion 24 adjacent the handleportion 20 and an elongated shaft 26 that extends from the proximalportion 24 and through the handle portion 20 and the guide tube 22. Aninflatable balloon 28 is mounted at the distal end of the ballooncatheter. The valve 12 is shown mounted on the balloon 28 in a crimpedstate having a reduced diameter for delivery to the heart via thepatient's vasculature.

The nose catheter 18 includes an elongated shaft 30 that extends throughthe proximal portion 24, the shaft 26, and the balloon 28 of the ballooncatheter. The nose catheter 18 further includes a nose piece 32 mountedat the distal end of the shaft 30 and adapted to receive a distal endportion of the balloon when the apparatus 10 is used to advance thevalve through the patient's vasculature to the implantation site.

As can be seen in FIGS. 2A and 2B, the balloon catheter 16 in theillustrated configuration further includes an inner shaft 34 (FIG. 2B)that extends from the proximal portion 24 and coaxially through theouter shaft 26 and the balloon 28. The balloon 28 can be supported on adistal end portion of the inner shaft 34 that extends outwardly from theouter shaft 26 with a proximal end portion 36 of the balloon secured tothe distal end of the outer shaft 26 (e.g., with a suitable adhesive).The outer diameter of the inner shaft 34 is sized such that an annularspace is defined between the inner and outer shafts along the entirelength of the outer shaft. The proximal portion 24 of the ballooncatheter can be formed with a fluid passageway 38 that is fluidlyconnectable to a fluid source (e.g., a water source) for inflating theballoon. The fluid passageway 38 is in fluid communication with theannular space between the inner shaft 34 and the outer shaft 26 suchthat fluid from the fluid source can flow through the fluid passageway38, through the space between the shafts, and into the balloon 28 toinflate the same and deploy the valve 12.

The proximal portion 24 also defines an inner lumen 40 that is incommunication with a lumen 42 of the inner shaft 34. The lumens 40, 42in the illustrated embodiment are sized to receive the shaft 30 of thenose catheter. The balloon catheter 16 also can include a coupler 44connected to the proximal portion 24 and a tube 46 extending from thecoupler. The tube 46 defines an internal passage which fluidlycommunicates with the lumen 40. The balloon catheter 16 also can includea slide support 48 connected to the proximal end of the coupler 44. Theslide support 48 supports and cooperates with an adjustment ring 50(FIGS. 1 and 4A-4B) of the nose catheter 18 to allow the nose catheterto be maintained at selected longitudinal positions relative to theballoon catheter 16, as described in greater detail below.

As shown in FIG. 2A, the outer surface of the outer shaft 26 can includeone or more annular grooves or notches 52 a, 52 b, 52 c spaced apartfrom each other along the proximal end portion of the shaft 26. Thegrooves cooperate with a locking mechanism 84 of the guide catheter 14(FIGS. 3A-3B) to allow the guide catheter 14 to be maintained atselected longitudinal positions relative to the balloon catheter 16, asdescribed in greater detail below.

The inner shaft 34 and the outer shaft 26 of the balloon catheter can beformed from any of various suitable materials, such as nylon, braidedstainless steel wires, or a polyether block amide (commerciallyavailable as Pebax®). The shafts 26, 34 can have longitudinal sectionsformed from different materials in order to vary the flexibility of theshafts along their lengths. The inner shaft 34 can have an inner lineror layer formed of Teflon® to minimize sliding friction with the nosecatheter shaft 30.

The guide catheter 14 is shown in greater detail in FIGS. 3A and 3B. Asdiscussed above, the guide catheter 14 includes a handle portion 20 andan elongated guide tube, or shaft, 22 extending distally therefrom. Theguide tube 22 defines a lumen 54 sized to receive the outer shaft 26 ofthe balloon catheter and allow the balloon catheter to slidelongitudinally relative to the guide catheter. The distal end portion ofthe guide tube 22 comprises a steerable section 56, the curvature ofwhich can be adjusted by the operator to assist in guiding the apparatusthrough the patient's vasculature, and in particular, the aortic arch.

The guide catheter desirably includes a cover, or shroud, 23 secured tothe distal end of the guide tube 22. The cover 23 in particularembodiments is sized and shaped to receive the valve 12 crimped aroundthe balloon and to abut against the proximal end surface of the nosepiece 32, which is adapted to cover a distal end portion of the balloon28 (as shown in FIG. 8A). Thus, when the apparatus is advanced to thedeployment site, the valve 12 and the balloon 28 can be completelyenclosed within the cover 23 and the nose piece 32.

As further shown in FIGS. 3A and 3B, the handle portion 20 includes amain body, or housing, 58 formed with a central lumen 60 that receivesthe proximal end portion of the guide tube 22. The handle portion 20 caninclude a side arm 62 defining an internal passage which fluidlycommunicates with the lumen 60. A stopcock 63 can be mounted on theupper end of the side arm 62.

The handle portion 20 is operatively connected to the steerable section56 and functions as an adjustment to permit operator adjustment of thecurvature of the steerable section 56 via manual adjustment of thehandle portion. In the illustrated embodiment, for example, the handleportion 20 includes an inner sleeve 64 that surrounds a portion of theguide tube 22 inside the handle body 58. A threaded slide nut 68 isdisposed on and slidable relative to the sleeve 64. The slide nut 68 isformed with external threads that mate with internal threads of anadjustment knob 70.

As best shown in FIGS. 5A and 5B, the slide nut 68 is formed with twoslots 76 formed on the inner surface of the nut and extending the lengththereof. As best shown in FIGS. 6A and 6B, the sleeve 64 is also formedwith longitudinally extending slots 78 that are aligned with the slots76 of the slide nut 68 when the slide nut is placed on the sleeve.Disposed in each slot 78 is a respective elongated nut guide 66 a, 66 b(FIG. 3B), which can be in the form of an elongated rod or pin. The nutguides 66 a, 66 b extend radially into respective slots 76 in the slidenut 68 to prevent rotation of the slide nut 68 relative to the sleeve64. By virtue of this arrangement, rotation of the adjustment knob 70(either clockwise or counterclockwise) causes the slide nut 68 to movelongitudinally relative to the sleeve 64 in the directions indicated bydouble-headed arrow 72.

One or more pull wires 74 connect the adjustment knob 70 to thesteerable section 56 to produce movement of the steerable section uponrotation of the adjustment knob. In certain embodiments, the proximalend portion of the pull wire 74 can extend into and can be secured to aretaining pin 80 (FIG. 3A), such as by crimping the pin 80 to the pullwire. The pin 80 is disposed in a slot 82 in the slide nut 68 (as bestshown in FIG. 5A). The pull wire 74 extends from pin 80, through a slot98 in the slide nut, a slot 100 in the sleeve 64, and into and through apull wire lumen in the shaft 22 (FIG. 3A). The distal end portion of thepull wire 74 is secured to the distal end portion of the steerablesection 56.

The pin 80, which retains the proximal end of the pull wire 74, iscaptured in the slot 82 in the slide nut 68. Hence, when the adjustmentknob 70 is rotated to move the slide nut 68 in the proximal direction(toward the proximal portion 24 of the balloon catheter), the pull wire74 also is moved in the proximal direction. The pull wire pulls thedistal end of the steerable section 56 back toward the handle portion,thereby bending the steerable section and reducing its radius ofcurvature. The friction between the adjustment knob 70 and the slide nut68 is sufficient to hold the pull wire taut, thus preserving the shapeof the bend in the steerable section if the operator releases theadjustment knob 70. When the adjustment knob 70 is rotated in theopposite direction to move the slide nut 68 in the distal direction,tension in the pull wire is released. The resiliency of the steerablesection 56 causes the steerable to return its normal, non-deflectedshape as tension on the pull wire is decreased. Because the pull wire 74is not fixed to the slide nut 68, movement of the slide nut in thedistal direction does not push on the end of the pull wire, causing itto buckle. Instead, the pin 80 is allowed to float within slot 82 of theslide nut 68 when the knob 70 is adjusted to reduce tension in the pullwire, preventing buckling of the pull wire.

In particular embodiments, the steerable section 56 in its non-deflectedshape is slightly curved and in its fully curved position, the steerablesection generally conforms to the shape of the aortic arch. In otherembodiments, the steerable section can be substantially straight in itsnon-deflected position.

The handle portion 20 can also include a locking mechanism 84 that isconfigured to retain the balloon catheter 16 at selected longitudinalpositions relative to the guide catheter 14. The locking mechanism 84 inthe illustrated configuration comprises a push button 86 having anaperture 88 through which the outer shaft 26 of the balloon catheterextends. As best shown in FIG. 3A, the button 86 has a distal endportion 90 that is partially received in an internal slot 92. A coilspring 94 disposed in the slot 92 bears against and resiliently urgesthe distal end portion 90 toward the shaft 26. The distal end portion 90can be formed with a small projection 96 that can nest within any ofgrooves 52 a, 52 b, 52 c on the shaft 26 (FIG. 2A). When one of thegrooves is aligned with the projection 96, the spring 94 urges theprojection into the groove to retain the shaft 26 at that longitudinalposition relative to the guide catheter (as depicted in FIG. 3A). Sincethe grooves in the illustrated embodiment extend circumferentiallycompletely around the shaft 26, the balloon catheter can be rotatedrelative to the guide catheter when the longitudinal position of theballoon catheter is locked in place by the button 86. The position ofthe balloon catheter can be released by pressing inwardly on the button86 against the bias of the spring 94 to remove the projection 96 fromthe corresponding groove on the shaft 26.

The handle portion 20 can have other configurations that are adapted toadjust the curvature of the steerable section 56. One such alternativehandle configuration is shown co-pending U.S. patent application Ser.No. 11/152,288 (published under Publication No. US2007/0005131), whichis incorporated herein by reference. Another embodiment of the handleportion is described below and shown in FIGS. 11-15.

FIGS. 7A and 7B show the guide catheter shaft 22 constructed inaccordance with one specific embodiment. The shaft 22 in the illustratedembodiment comprises a tubular inner liner 104 made of a low-frictionpolymeric material, such as PTFE. The liner 104 is sized to allow adeflated balloon 28 and the balloon catheter shaft 26 to be insertedtherethrough. A smaller conduit, or liner 106, which extends along theoutside of the inner liner 104, defines a lumen through which the pullwire 74 extends. An outer layer 108 surrounds the liners 104, 106 andimparts the desired flexibility and stiffness to the shaft 22.

The outer layer 108 in the illustrated embodiment comprises a braidedlayer formed from braided metal wire 110 wound around the liner 104 andthe conduit 106, and a polymeric material 112 surrounding andencapsulating the braided metal wire layer. In particular embodiments,the shaft can be formed by forming the liners 104, 106, placing theliners side-by-side in a parallel relationship relative to each other,wrapping the metal wire around the liners to form the braided layer,placing a polymeric sleeve over the braided layer, and reflowing thesleeve to form a uniform laminate layer 108 surrounding the liners. Incertain embodiments, the polymeric material 112 comprises any suitablematerial, but desirably comprises a thermoplastic elastomer, such asPebax®. The braided metal layer can be constructed from stainless steelwire.

As best shown in FIG. 7A, the shaft 22 desirably comprises a relativelystiff section 114 extending from the proximal end 116 of the shaft tothe proximal end 118 of the steerable section 56. In particularembodiments, the length of the steerable section 56 comprises about ¼ ofthe overall length of the shaft 22. In a working embodiment, the overalllength of the shaft 22 is about 45 inches (including the steerablesection) and the length of the steerable section is about 11.7 inches,although the overall length of the shaft and/or the length of thesteerable section can be varied depending on the particular application.

The steerable section 56 of the shaft desirably is formed from arelatively soft durometer material 112 to allow the steerable section tobend upon adjustment of the adjustment knob 70, as described above. Thestiff section 114 desirably is formed from a relatively stifferpolymeric material 112 that resists bending when the pull wire istensioned by the adjustment knob 70. The stiff section 114 desirablyexhibits sufficient rigidity to allow the operator to push the apparatus10 through a potentially constricting body vessel. In particularembodiments, the polymeric material 112 of the steerable sectioncomprises 55D Pebax® and the polymeric material 112 of the remainingsection 114 of the shaft comprises 72D Pebax®, which is stiffer than 55DPebax®.

In alternative embodiments, the metal braided layer in the steerablesection 56 can be replaced with a metal coil (e.g., a stainless steelcoil) disposed on the inner liner 104 to enhance the flexibility of thesteerable section. Thus, in this alternative embodiment, the braidedmetal layer extends along the stiff section 114 and the metal coilextends along the steerable section 56. In another embodiment, the metalbraided layer in the steerable section 56 can be replaced with astainless steel hypotube that is formed with laser-cut,circumferentially extending openings, such as disclosed in co-pendingU.S. patent application Ser. No. 11/152,288.

As shown in FIG. 7C, the distal end of the shaft 22 can include aflared, or enlarged, end portion 116. The outer diameter D of the endportion 116 is equal to or about the same as the outer diameter of thecrimped valve 12 supported on the balloon 28. Accordingly, when thevalve 12 is advanced through an introducer sheath, the end portion 116pushes against the crimped valve 12, rather than the balloon 28. Thisminimizes inadvertent movement between the balloon catheter and thevalve, which can cause the position of the valve on the balloon to move.In particular embodiments, the shaft 22 has an outer diameter of about16 F to about 18 F and the end portion 116 has an outer diameter D ofabout 22 F. The enlarged end portion 116 can be made of any of varioussuitable materials. For example, the end portion 116 can be molded fromPebax® (e.g., 55D Pebax®) and reflowed on the end portion of thesteerable section 56.

As mentioned above, the distal end of the pull wire 74 is secured at thedistal end of the steerable section 56. As best shown in FIG. 7C, thiscan be achieved by securing the distal end portion of the pull wire 74to a metal ring 118 embedded in the outer layer 108 of the shaft, suchas by welding the pull wire to the metal ring.

Although not shown in FIGS. 7A-7C, the guide catheter shaft 22 caninclude a cover 23 for covering the valve 12 and the balloon 28 (or aportion thereof) during delivery of the valve. As explained below, theuse of an introducer sheath can be optional if the valve is covered uponinsertion into the patient's vasculature.

Referring to FIGS. 4A and 4B, and as discussed briefly above, the nosecatheter 18 includes an adjustment ring 50 at its proximal end and anose piece 32 at its distal end, and an elongated shaft 30 extendingtherebetween. The shaft 30 desirably is formed with a lumen 120extending the length of the shaft for receiving a guide wire 140 (FIG.8A) so that the apparatus 10 can be advanced over the guide wire afterit is inserted into the delivery path in the body. As shown in FIGS. 4Aand 4B, the nose piece 32 desirably is formed with an opening or cavity122 sized and shaped to receive at least a distal end portion of theballoon 28.

As best shown in FIG. 4A, the adjustment ring 50 is disposed on andslidable relative to the slide support 48 of the balloon catheter, whichfunction as a locking or retaining mechanism for retaining the nosecatheter at selective longitudinal positions relative to the ballooncatheter. Explaining further, the shaft 30 extends through and isfixedly secured to a shaft support 124 disposed within the side support48. The adjustment ring 50 is secured to the shaft support 124 by screws126, which extend through elongated slots 128 a, 128 b in the slidesupport 48. Slots 128 a, 128 b extend longitudinally along the length ofthe slide support 48. Hence, when the adjustment ring 50 is slidlongitudinally along the length of the slide support 48 (in thedirections indicated by double-headed arrow 130), the shaft support 124and the shaft 30 are caused to move in the same direction so as toadjust the longitudinal position of the nose catheter relative to theballoon catheter.

The slot 128 a is formed with circumferentially extending notches 132a-132 d and the slot 128 b is formed with similar circumferentiallyextending notches 134 a-134 d opposite the notches 132 a-132 d. Thus,for each notch 132 a-132 d, there is a corresponding, diametricallyopposed notch 134 a-134 d extending from slot 128 b. To retain thelongitudinal position of the nose catheter relative to the ballooncatheter, the adjustment ring 50 is moved to align the screws 126 with apair of diametrically opposed notches and then rotated slightly toposition the screws 126 in the notches. For example, FIG. 4A shows thescrews 126 positioned in notches 132 b and 134 b. The notches restrictmovement of the screws 126, and therefore the shaft support 124 and theshaft 30, in the distal and proximal directions.

In the illustrated embodiment, each slot 128 a, 128 b is formed withfour notches. When the screws 126 are positioned in notches 132 c, 134 cor in notches 132 d, 134 d, the nose piece 32 is retained at a positioncovering a distal end portion of the balloon 28 and abutting the cover23 of the guide catheter 14 such that the balloon 28 and the valve 12are completely enclosed by the cover 23 and the nose piece 32 (FIG. 8A).When the screws 126 are positioned in notches 132 b, 134 b, the nosepiece 32 is retained at a position spaced distally a first distance fromthe balloon 28 so that the valve can be deployed by inflating theballoon without inference from the nose piece (FIG. 8C). When the screwsare positioned in notches 132 a, 134 a, the nose piece is retained at aposition spaced distally a second distance, greater than the firstdistance, from the balloon 28. In this position, the balloon 28 can berefolded inside the cover 23 (after valve deployment) withoutinterference from the nose piece.

The valve 12 can take a variety of different forms. In particularembodiments, the valve generally comprises an expandable stent portionthat supports a valve structure. The stent portion desirably hassufficient radial strength to hold the valve at the treatment site andresist recoil of the stenotic native valve leaflets. Additional detailsregarding balloon expandable valve embodiments can be found in U.S. Pat.Nos. 6,730,118 and 6,893,460, each entitled IMPLANTABLE PROSTHETICVALVE, which are incorporated by reference herein. It will also beappreciated that the delivery system may be used with self-expandingprosthetic valves. For example, when using a self-expanding valve, apusher may be used to assist in ejecting the self-expanding valve from adelivery sleeve that maintains the valve in its compressed state.

When the valve 12 is used to replace the native aortic valve (or apreviously implanted, failing prosthetic aortic valve), the valve 12 canbe implanted in a retrograde approach where the valve, mounted on theballoon in a crimped state, is introduced into the body via the femoralartery and advanced through the aortic arch to the heart. In use, aguide wire 140 (FIG. 8A) can be used to assist in advancing the deliverydevice 10 through the patient's vasculature. The guide wire 140 can beplaced in the body vessel through a dilator (not shown), which expandsthe inner diameter of the body vessel for introducing the deliverydevice. Dilator diameters range between, for example, 12 and 22 French.

As noted above, and as shown in FIG. 8A, the valve 12 can be positionedinside the cover 23 with the nose piece 32 covering the distal endportion of the balloon 28 and abutting the distal end of the cover 23.The adjustment ring 50 of the nose catheter can be locked in place toretain nose piece 32 against the cover 23 during delivery. In thisposition, the nose catheter desirably is placed in slight tension withthe nose piece 32 held tightly against the cover 32 to inhibitseparation of the nose piece from the cover while tracking the devicethrough the vasculature and during removal of the delivery apparatusfrom the body.

Advantageously, because the valve 12 in the illustrated embodiment canbe completely covered by the cover 23, an introducer sheath is notneeded to introduce the valve into the body vessel. An introducer sheathhaving a diameter of about 22 to 24 French typically is used in aretrograde procedure. In contrast, the cover 23 desirably has an outerdiameter that is less than the outer diameter of the introducer sheath,and in particular embodiments, the outer diameter of the cover 23 is inthe range of about 0.260 inch to about 0.360 inch, with about 0.330 inchbeing a specific example. By reducing the overall diameter of thedevice, it is less occlusive to the femoral artery and the patient's legcan remain well perfused during the procedure. Further, because thecover 23, which represents the largest diameter of the delivery device,need only be in contact with the femoral and iliac arteries for only avery short period of time, trauma to these vessels can be minimized.

Although less desirable, in other embodiments the cover 23 can beshorter in length so that less of the outer surface of the valve and theballoon is covered by the cover 23 during delivery. For example, thecover 23 can be dimensioned to extend over only a proximal end portionof the balloon or a proximal end portion of the valve.

As the delivery apparatus 10 is advanced over the guide wire 140 andthrough the aortic arch, the guide catheter 14 is used to “steer” theapparatus away from the inner surface of the aorta. The tapered distalend portion of the nose piece 32 assists in tracking through the femoraland iliac arteries, as well as provides atraumatic tracking through overthe aortic arch and smooth crossing of the native aortic valve. In priordelivery systems, it is known to fix a nose piece at the distal end ofthe balloon catheter, which increases the length of the portion of thedevice that cannot be curved by operation of a guide catheter. Incontrast, the nose piece 32 in the illustrated embodiment is mounted onseparate nose catheter 18 that can be moved relative to the valve 12.The nose piece 32 therefore can be mounted over the distal end portionof the balloon during delivery in order to minimize the length of thenon-steerable section at the distal end of the delivery device. Thisallows for easier tracking through the aortic arch with little or nocontact between the end of the delivery device and the inner walls ofthe aorta. In particular embodiments, the length L (FIG. 8A) of thenon-steerable section at the end of the delivery device is about 6 cm orless.

Using conventional fluoroscopy, the operator can track the positions ofmarker bands 142 (FIGS. 2A and 2B) on the guide wire shaft 34 in orderto position the valve at the implantation site. After the valve 12 isadvanced into the aortic annulus, the nose catheter can be moveddistally relative to the balloon catheter to advance the nose piece 32distally away from the balloon 28 (FIG. 8B) and the guide catheter canbe moved proximally relative to the balloon catheter to expose the valve12 from the cover 23 (FIG. 8C). As explained above, the longitudinalpositions of the nose catheter and the guide catheter can be fixedrelative to the balloon catheter while the operator adjusts the positionof and then deploys the valve 12. Inflation of the balloon 28 iseffective to expand the valve 12 to engage the native valve leaflets.The balloon 28 can then be deflated and retracted back into the cover 23and the nose piece 32 can be pulled back over the distal end portion ofthe balloon. The entire delivery apparatus can then withdrawn back overthe guide wire 140 and removed from the body, after which the guide wirecan be removed from the body.

FIG. 9 shows an alternative embodiment of the delivery apparatus 10. Inthis embodiment, the guide catheter 14 is not provided with a cover 23(as previously illustrated in FIGS. 3A and 3B) and instead an introducersheath 150 can be used to introduce the delivery apparatus into thebody. As best shown in FIGS. 10A and 10B, the introducer sheath 150 inthe illustrated embodiment includes an introducer housing 152 and anintroducer sleeve 154 extending from the housing 152. The housing 152houses a sealing valve 166. In use, the sleeve 154 is inserted into abody vessel (e.g., the femoral artery) while the housing 152 remainsoutside the body. The delivery apparatus 10 is inserted through aproximal opening 168 in the housing, the sealing valve 166, the sleeve154 and into the body vessel. The sealing valve 166 sealingly engagesthe outer surface of the guide catheter shaft 22 to minimize blood loss.In certain embodiments, the sleeve 154 can be coated with a hydrophiliccoating and extends into the body vessel about 9 inches, just past theiliac bifurcation and into the abdominal aorta of the patient.

The sleeve 154 can have a tapered section 156 that tapers from a firstdiameter at a proximal end 158 to a second, smaller diameter at a distalend 160. A reduced diameter distal end portion 162 extends from thetapered portion 156 to the distal end of the sleeve 154. The taperedportion 156 provides for a smoother transition between the outer surfaceof the sleeve 154 and the outer surface of the guide shaft 22 of theguide catheter 14. The tapered portion 156 also allows for variableplacement of the sleeve 154 in the patient's vasculature to helpminimize complete occlusion of the femoral artery.

FIGS. 11-15 show an alternative embodiment of a handle portion,indicated at 200, that can be used in the guide catheter 14 (FIGS. 1 and3A), in lieu of handle portion 20. The handle portion 200 in theillustrated embodiment includes a main housing 202 and an adjustmentlever 204 pivotably connected to the housing 202. The lever 204 can bepivoted distally and proximally (as indicated by double-headed arrow 206in FIG. 13) to adjust the curvature of the shaft 22, as furtherdescribed below.

As best shown in FIG. 14, the housing 202 can be formed from first andsecond housing portions 208, 210 that can be secured to each other usinga suitable adhesive, mechanical fasteners, a snap fit connection, orother suitable techniques. Disposed within the housing 202 is a sealhousing 212 that has a central bore 226 extending therethrough. Thedistal end portion of the bore 226 can form an enlarged portion thatreceives the proximal end portion 214 of the shaft 22. The shaft 22extends from the seal housing 212 through the main housing 202 and outof a nose piece 228 connected to the distal end of the main body 202. Anend piece 216 can be connected to the proximal end of the seal housing212 with a seal 218 captured between these two components. As best shownin FIG. 15, the end piece 216 can be formed with a stepped bore shapedto receive the seal 218 and an end portion of the seal housing 212. Theseal 218 can be made of a suitable elastomer, such as silicon. The shaft26 of the balloon catheter 16 extends through the end piece 216, acentral opening in the seal 218, the seal housing 212, and the guidecatheter shaft 22. The seal housing 212 can be formed with a flush port220 that is in fluid communication with the central bore 226. The flushport 220 receives one end of a flexible tube 222. The opposite end ofthe tube 222 can be connected to a stopcock 224 (FIG. 11).

As shown in FIG. 14, the lever 204 in the illustrated configurationcomprises first and second lever portions 230, 232, respectively,mounted on opposite sides of the main housing 202. The inner surface ofeach lever portion can be formed with an annular groove 274 adapted toreceive a respective O-ring 234. The lever portion 230 can be coupled toa pulley 236 mounted in the housing to produce rotation of the pulleyupon pivoting movement of the lever portion. For example, the leverportion 230 can be formed with a projection 238 that extends through thehousing portion 208 and into a complementary shaped recess 240 (FIG.16A) in the pulley 236. The projection 236 can be formed with flats onits outer surface that engage corresponding flats in the recess 240 toproduce rotation of the pulley when the lever is activated. The pulley236 can also be formed with a non-circular recess or opening 242 that isshaped to receive one end portion of a shaft 244 (FIG. 14). The oppositeend of the shaft 244 extends through the second housing portion 210 andinto a complementary shaped recess or opening 246 of the lever portion232 (FIG. 17). In the illustrated configuration, the end portions of theshaft 244 and the corresponding openings 242 and 246 are hexagonal toinhibit relative rotation between the shaft 244, the pulley 236, and thelever portion 232, although various other non-circular shapes can beused. Alternatively, the end portions of the shaft and the openings 242,246 can be circular if the shaft is otherwise fixed against rotationrelative to the pulley and the lever portion.

Upper and lower cross-bars 248, 250, respectively, are connected to andextend between respective upper and lower ears of the first and secondlever portions 230, 232. Screws 252 extending through the ears of thelever portions 230, 232 and tightened into the cross-bars 248, 250 canbe used to secure the components of the lever 204 to the main body 202.A screw 254 can extend through the lever portion 230, the housingportion 208, and into a threaded opening in the shaft 244. An adjustmentknob 266 can be fixedly secured to a screw 268, which can extend throughthe lever portion 232, the housing portion 210, and into a threadedopening in the opposite end of the shaft 244. The screw 268 can befixedly secured to the adjustment knob, for example, by adhesivelysecuring the head of the screw within a recess (not shown) on the innersurface of the adjustment knob. Consequently, the adjustment knob 266can be manually rotated to loosen or tighten the screw into the shaft244 to adjust the rotational friction of the pulley 236.

Referring again to FIG. 15, a pull wire 74 extends through a pull wirelumen in the shaft 22 and extends from the shaft inside of the mainhousing 202. A flexible tension member 256, such as a piece of string,is tied off or otherwise connected to at one thereof to the end of thepull wire 74. The tension member 256 extends around a cross-member 258,partially around the outer circumference of the pulley 236, through aradially extending opening 260 in the pulley and is tied off orotherwise connected to the shaft 244 adjacent the center of the pulley236. As shown in FIGS. 16A and 16B, the pulley 236 can be formed with anannular groove or recess 262 adapted to receive the tension member 256.

Explaining the operation of the handle portion 200, FIG. 18A shows theadjustment lever 204 in a forward-most position. In this position, thesteerable section 56 of the shaft 22 is in its normal, non-deflectedstate (e.g., straight, such as shown in FIG. 1, or slightly curved). Asthe lever 204 is pivoted rearwardly, in the direction of arrow 264, thepulley 236 is rotated clockwise in the illustrated embodiment, causingthe tension member to wind around the pulley and pull the pull wire 74rearwardly. The pull wire 74, in turn, pulls on the distal end of theshaft to adjust the curvature of the steerable section 56, in the mannerpreviously described. FIG. 18B shows the lever 204 in a rearward-mostposition corresponding to the fully curved position of the steerablesection of the shaft 22.

The rotational friction of the pulley 236 is sufficient to hold the pullwire taut, thus preserving the shape of the bend in the steerablesection if the operator releases the adjustment lever 204. When thelever 204 is pivoted back toward the forward-most position (FIG. 18A),tension in the pull wire is released. The resiliency of the steerablesection 56 causes the steerable section to return to its normal,non-deflected shape as tension on the pull wire is released. Because thetension member 256 in the illustrated embodiment does not apply apushing force to the pull wire, movement of the lever 204 toward theforward-most position does not cause buckling of the pull wire. Further,as noted above, the adjustment knob 266 can be adjusted by the operatorto vary the rotational friction of the pulley 236. The rotationalfriction desirably is adjusted such that if the guide catheter is pulledback inadvertently while in the patient's vasculature, the pulley canrotate toward the forward-most position under a forward pulling force ofthe pull wire (as indicated by arrow 270 in FIG. 18B) to allow thesteerable section to straighten out as it is pulled through thevasculature, minimizing trauma to the vasculature walls.

Advantageously, the adjustment lever 204 in the illustrated embodimentprovides a substantially 1:1 deflection of the steerable section inresponse to movement of the lever; that is, rotation of the lever 204causes a substantially 1:1 movement of the pull wire and therefore thesteerable section 56. In this manner, the adjustment lever 204 providesthe operator tactile feedback of the curvature of the steerable sectionto facilitate tracking through the vasculature. In addition, the leveris ergonomically positioned for maintaining the proper orientation ofthe guide catheter during use. Another advantage of the illustratedhandle portion 200 is that the proximal portion 24 of the ballooncatheter 16 (FIG. 2B) or a portion thereof can seat within the end piece216 to minimize the working length of the balloon catheter.

FIGS. 19A and 19B illustrate an alternative nose catheter 300, accordingto one embodiment, that can used with the delivery apparatus 10 (FIG.1), in lieu of the nose catheter 18. The nose catheter 300 in theillustrated configuration includes a nose piece or valve cover 302connected to a nose catheter shaft 304. The valve cover 302 is adaptedto cover the balloon 28 and a valve 12 mounted on the balloon. Thus, inthis embodiment, the guide catheter 14 need not have a cover 23 (FIG.8A) to cover the valve during delivery. The shaft 304 is fixedly securedat its distal end to the distal end of the cover 302 and extends throughthe balloon 28 and the balloon catheter shaft 26. The shaft 304 can havea lumen to receive a guide wire 140. The shaft 304 can movelongitudinally relative to the balloon catheter and the guide catheter,much like the nose catheter 18 previously described.

As best shown in FIG. 19A, the cover 302 has a proximal end portion 306formed with a plurality of slits defining triangular flaps 308. Theflaps 308 can flex radially outwardly from each other to form an openinglarge enough to allow passage of the balloon 28 and the valve 12 when itis desired to deploy the valve. The proximal end portion 306 can betapered as shown to facilitate retraction of the cover 302 back into anintroducer sheath. The tapered shape of the end portion 306 alsoprovides an atraumatic surface to minimize trauma to the vasculaturewalls when the delivery apparatus is withdrawn from the body. The coveralso can have a tapered distal end portion 310 to assist in trackingthrough the femoral and iliac arteries, as well as provide atraumatictracking through the aortic arch and smooth crossing of the nativeaortic valve.

The cover 302 desirably is made from a flexible material, such as nylon,Pebax®, or PET and can have a wall thickness in the range of about0.0015 inch to about 0.015 inch. By making the cover 302 sufficientlyflexible, the only relatively stiff, non-flexible section along theportion of the delivery apparatus advanced through the patient'svasculature is the section of the balloon covered by the valve. Thisgreatly enhances the ability of the delivery apparatus to follow thepath of the guide wire 140 as it is advanced through tortuous bodyvessels.

In use, the delivery apparatus is advanced over the guide wire 140 untilthe valve is positioned at or near the deployment location. The nosecatheter 300 is then advanced distally relative to the balloon catheter16 to uncover the balloon and the valve 12, as illustrated in FIG. 19C.As the cover 302 is advanced distally, the balloon and the valve canpass through the proximal opening formed by flaps 308. Once the valve 12is exposed, the balloon 28 can be inflated to deploy the valve.

FIG. 20A shows a modification of the guide catheter 14 where the valvecover 23 is replaced with an expandable mesh basket or cover 400connected to the distal end of the guide catheter shaft 22. The cover400 is sized and shaped to cover the valve 12 and the balloon 28. Thus,in this embodiment, a nose catheter (e.g., nose catheter 18) need not beused. The cover 400 can have a braided mesh construction formed frommetal wire (e.g., Nitinol or stainless steel wires).

One or more ribbon wires 402 are connected to the distal end 404 of thecover 400 and extend through respective lumens in the guide cathetershaft 22 along the length thereof (FIG. 20B). The wires 402 can be, forexample, 0.003 inch×0.020 inch Nitinol ribbon wire. The wires 402 areconnected at their proximal ends to a handle portion of the guidecatheter that allows the operator to apply pushing or pulling forces tothe wires. Pushing the wires 402 forward, in the direction of arrow 406,causes the cover to collapse over the balloon 28 and the valve 12 toprovide a smooth tracking profile. Pulling the wires 402 rearward, inthe direction of arrow 408, causes the cover to expand and allows theballoon and valve to be advanced outwardly through an opening at thedistal end 404 of the cover 400.

In use, the cover 400 is placed in a collapsed state covering the valveand the balloon for delivery through the patient's vasculature to thedeployment site. The wires 402 are then pulled in the proximal direction(as indicted by arrow 408) to expand the cover 400. The guide cathetercan then be pulled in the proximal direction to advance the balloon andthe valve from the distal end of the cover. Alternatively, the ballooncatheter 16 can be advanced distally relative to the guide catheter 14to advance the balloon and the valve from the cover 400.

FIGS. 21A-21C show an alternative embodiment of a delivery apparatus,indicated at 500. The delivery apparatus 500 allows a valve 12 to bemounted on a balloon 28 of a balloon catheter inside a body vessel. Theballoon catheter can have a construction similar to the balloon cathetershown in FIGS. 2A and 2B except that in the embodiment of FIGS. 21A-21B,the balloon catheter shaft 26 has a distal end portion 504 that extendsdistally from the balloon 28 and an annular tapered wedge 502 isdisposed on the distal end portion 504 adjacent the balloon. The taperedwedge 502 functions to expand the valve to facilitate positioning thesame on the balloon inside the body, as further described below. Thewedge 502 desirably is made from a low-friction material, such as nylon,to allow the valve to easily slide over the wedge and onto the balloon.

The delivery apparatus includes a nose catheter comprising a shaft 506and a nose piece 508 connected to the distal end of the shaft 506. Thenose catheter shaft 506 can have a guide wire lumen to receive a guidewire 140 so that the apparatus can be advanced over the guide wire withthe guide wire passing through the lumen. The delivery apparatus 500 canfurther include a guide catheter comprising a guide catheter shaft 22and an elongated cover 510 extending from the distal end of the shaft22. The nose catheter, balloon catheter, and guide catheter are moveablelongitudinally relative to each other and can have locking mechanisms atthe proximal end of the apparatus for retaining the catheters atselected longitudinal positions relative to each other, as described indetail above.

As shown in FIG. 21A, the valve 12 is initially mounted in a crimpedstate on the nose catheter shaft 506 between the nose piece 508 and thetapered wedge 502, rather than on the balloon prior to inserting thedelivery apparatus into the body. The valve is crimped onto the nosecatheter shaft such that that valve can still move along the shaft whenit is desired to place the valve on the balloon 28. The nose piece 508can be formed with a stepped bore comprising a first bore portion 512and a second, enlarged bore portion 514 at the proximal end of the nosepiece. The stepped bore can be formed with an annular shoulder 516extending between the first and second bore portions and adapted toengage the distal end of the valve 12 when the valve is inserted intothe second portion 514. The nose piece 508 can have an outer surfacethat tapers in a direction toward the distal end of the nose piece 508to provide atraumatic tracking through tortuous vasculature. The cover510, which can be optional, is adapted to extend over and cover theballoon 28, the wedge 502, and at least a proximal end portion of thevalve 12 when the valve is positioned on the nose catheter shaft fordelivery. In the illustrated embodiment, the distal end of the cover 510can be positioned to abut the proximal end of the nose piece 508 so asto completely enclose the valve during delivery. In alternativeembodiments, the cover 510 can be shorter in length so that less of theouter surface of the valve or the balloon is covered during delivery.

The nose piece 508, when moved proximally relative to the ballooncatheter (in the direction indicated by arrow 518), pushes the valve 12over the wedge 502 and onto the balloon 28. As the valve passes over thewedge, the valve expands slightly to facilitate positioning the same onthe balloon. The balloon catheter shaft 26 can have radiopaque markers520 (FIG. 21A) to assist the operator in aligning the valve at theproper location on the balloon. The nose piece can have an outer layer522 formed from a relatively soft and flexible material and an innerlayer 524 formed from a relatively harder material. The inner layer 524in the illustrated embodiment forms the shoulder 516 and the innersurface of the first bore portion 512. In this manner, the nose pieceexhibits sufficient rigidity to push the valve 12 over the wedge andonto the balloon and provides a soft outer surface to minimize trauma tothe body vessels. For example, the outer layer 522 can be made of 55DPebax® and the inner layer can be made of 72D Pebax®, which is stifferthan 55D Pebax®.

The section of the delivery apparatus mounting the valve typicallydefines the maximum outer diameter of the apparatus inserted into thebody. By mounting the valve 12 on the nose catheter shaft rather than onthe balloon prior to insertion into the body, the valve 12 can becrimped to a smaller diameter than if the valve is mounted on theballoon. Accordingly, the maximum outer diameter of the deliveryapparatus can be reduced for insertion into and through the vasculature.As noted above, by reducing the maximum diameter of the deliveryapparatus, it is less occlusive to the femoral artery and therefore thepatient's leg can remain well perfused during the procedure. In certainembodiments, the maximum outer diameter of the cover 510 and the nosepiece 508 (at its proximal end) is about 0.223 inch, which is themaximum diameter of the portion of the delivery apparatus that isinserted into the body. The wedge 502 can have a diameter at itsproximal end of about 0.120 inch and the guide catheter shaft 22 canhave an outer diameter of about 0.184 inch.

Explaining now the operation of the delivery apparatus 500, according toone embodiment, the valve 12 is initially mounted on the nose cathetershaft and inserted into the nose piece 508 and the cover 510. After aguide wire 140 is inserted into the body, the proximal end of the wireextending from the body can be inserted into the distal end of the guidewire lumen and the delivery apparatus 500 can be inserted into a bodyvessel (e.g., the femoral artery) and advanced through the body (asdepicted in FIG. 21A). Alternatively, an introducer sheath can beinserted first into the body vessel, for example if a cover 510 is notprovided to cover the valve 12. Subsequent to inserting the introducersheath, the delivery apparatus can be inserted through the introducersheath and into the body vessel.

When the distal end of the delivery apparatus is advanced to a locationthat is convenient to slide the valve 12 onto the balloon, the guidecatheter is retracted proximally relative to the balloon catheter toadvance the valve and the balloon from the cover 510. For example, ifimplanting a prosthetic valve within the native aortic valve, the valveand the balloon can be advanced into the ascending aorta or into theleft ventricle where the valve can then be moved onto the balloon. Inany case, as shown in FIG. 21B, the nose catheter can be retractedproximally to advance the valve over the wedge 502 and onto the balloon28. Markers 520 (FIG. 21A) can be used to center the valve on theballoon. After mounting the valve on the balloon, the nose catheter canbe advanced distally so as not to interfere with inflation of theballoon, as shown in FIG. 21C. The valve can then be positioned at theimplantation site (e.g., within the native aortic valve) and deployed byinflating the balloon.

FIGS. 22A and 22B show a modification of the delivery apparatus 10(FIGS. 1-8). In the embodiment of FIGS. 22A and 22B, the cover 23 has agenerally tubular shape but is provided in a rolled up state on thedistal end portion of the guide catheter shaft 22. After the valve 12 ismounted on the balloon 28, the cover can be unrolled over the valve 12for insertion into and through the patient's vasculature. The operationof the deliver apparatus shown in FIGS. 22A and 22B is otherwiseidentical to the operation of the delivery apparatus 10 described abovewith reference to FIGS. 8A-8C.

FIGS. 23A and 23B show an embodiment of an improved introducer sheath,indicated at 600, that can be used to facilitate insertion of a deliveryapparatus into a body vessel. The introducer sheath 600 is particularlysuited for use with a delivery apparatus that is used to implant aprosthetic valve, such as the embodiments of delivery apparatusdescribed herein. The introducer sheath 600 also can be used tointroduce other types of delivery apparatus for placing various types ofintraluminal devices (e.g., stents, stented grafts, etc.) into manytypes of vascular and non-vascular body lumens (e.g., veins, arteries,esophagus, ducts of the biliary tree, intestine, urethra, fallopiantube, other endocrine or exocrine ducts, etc.). The example illustratedin FIG. 23A shows the distal end portion of a delivery apparatus used toimplant a prosthetic valve 12. The delivery apparatus comprises aballoon catheter and a guide catheter. The balloon catheter comprises ashaft 26 and a balloon 28 mounted on the distal end portion of theshaft. The guide catheter comprises a shaft 22 extending over theballoon catheter shaft 26. The remaining portions of the ballooncatheter and the guide catheter can be constructed according to theembodiment shown in FIGS. 1-8.

A conventional introducer sheath typically requires a tubular loader tobe inserted through the seals in the sheath housing to provide anunobstructed path for a valve mounted on a balloon catheter. The loaderextends from the proximal end of the introducer sheath, therebyincreasing its working length, and decreasing the available workinglength of a delivery apparatus that can be inserted into the body. Theintroducer sheath 600 includes a integrated loader tube housed in thesheath housing to reduce the working length of the sheath, and thereforeincrease the available working length of a delivery apparatus that canbe inserted into the body.

For example, the illustrated sheath 600 includes a seal housing 602 anda tubular sleeve 604 extending distally from the housing. The sealhousing 602 houses one or more sealing valves, such as a cross-slitvalve 606, a disc valve 608, and a hemostatic valve 610 as shown in theillustrated embodiment. The valves desirably are fabricated from aresilient biocompatible material, such as polyisoprene, although similarbiocompatible materials also can be used. The valves 606, 608, 610 arefurther shown and described in U.S. Pat. No. 6,379,372, which isincorporated herein by reference. A spacer 612 can be interposed betweenthe disc valve 608 and the cross-slit valve 606.

Coupled to the proximal end of the seal housing is an end piece 614adapted to move longitudinally along the length of the seal housing. Inthe illustrated embodiment, the end piece has a tubular body formed withinternal threads 616 that engage external threads 618 formed on theouter surface of the seal housing 602. Thus, rotation of the end piece614 moves the same inwardly and outwardly relative to the seal housing.The end piece 614 has a central opening 620 and an elongated loader tube622 fixedly secured to the proximal end portion of the end piece andextending distally therefrom. The opening 620 and the loader tube 622are dimensioned to permit passage of the valve 12 (or other prosthesis)mounted on the delivery apparatus. The end piece 614 also houses a seal624 having a central opening aligned with the opening 620. The seal 624sealingly engages the outer surface of the delivery apparatus when it isinserted into the introducer sheath 600.

As noted above, the end piece 614 can be adjusted inwardly and outwardlyrelative to the seal housing 602. Adjusting the end piece 614 from theextended position shown in FIG. 23A to the retracted position shown inFIG. 23B moves the loader tube 622 through the seals 606, 608, 610 toprovide an unobstructed path for the valve 12 to pass through theintroducer sheath. Because the loader tube does not extend behind theend piece, as in a conventional introducer sheath, the loader tube doesnot decrease the available working length of the delivery apparatus thatcan be inserted into the vasculature.

In use, the introducer sheath 600 in the extended position shown in FIG.23A can be placed on a previously inserted guide wire 140 and advancedthereon until the sleeve 604 extends into a body vessel a desireddistance. The delivery apparatus can then be inserted through theopening 620 to position the valve 12 in the loader tube 622 with theseal 624 forming a fluid tight seal around the guide catheter shaft 22.Subsequently, the end piece 614 is rotated to slide the loader tube 622through the valves 606, 608, 610 (FIG. 23B), thus placing the deliveryapparatus in communication with the lumen of the sleeve 604 and the bodyvessel in which the sleeve is inserted. Advantageously, this approachsimplifies the loading process and reduces the number of steps and partsrequired to load the valve into the sheath.

In an alternative embodiment of the introducer sheath 600, the sealhousing 602 can have internal threads that engage external threads onthe end piece 614. The end piece can be rotated to adjust the positionof the loader tube 622 as previously described. In addition, the pitchof the threads on the seal housing and the end piece can be varied tovary the amount of rotational movement required to extend the loaderthrough the sealing valves. In another embodiment, the end piece 614 canbe slidingly positionable along the length of the seal housing bypushing and pulling the end piece without rotating the same.

FIGS. 24A and 24B show another embodiment of a nose catheter, indicatedat 700, that can be used in the delivery apparatus 10 (FIG. 1). The nosecatheter 700 includes a nose piece 702 and a nose catheter shaft 704.The nose piece 702 has a distal end 706 connected to the nose cathetershaft 704 and a proximal end connected to the distal end of a ballooncatheter shaft 26. The nose piece 702 comprises a balloon or similarstructure formed from a thin, flexible material, such as nylon or PET,capable of assuming an inverted shape covering a valve 12 and a balloon28 or portions thereof when the nose piece 702 is urged against theballoon 28. For example, the nose piece 702 can have a structure similarto the balloon 28.

The nose catheter shaft 704 is slidable relative to the balloon cathetershaft 26, although the proximal end of the nose piece 702 is connectedto the balloon catheter shaft. Hence, as the nose catheter shaft 704 ismoved proximally relative to the balloon catheter shaft 26 (in thedirection of arrow 710) from a first, extended position (FIG. 24B)toward a second, retracted position (FIG. 24A), the nose piece 702 isurged against the distal end of the balloon catheter shaft 26, causingthe nose piece 702 to assume an inverted position covering a portion ofthe outer surface of the balloon 28 and the valve 12. Similarly, it canbe seen that moving the balloon catheter shaft distally relative to thenose catheter shaft from the extended position shown in FIG. 24B also iseffective to cause the nose piece to assume an inverted position overthe balloon and the valve.

In use, the nose piece 702 is initially placed in the inverted positionshown in FIG. 24A to provide a smooth tracking profile during deliveryof the valve through the patient's vasculature. At or near theimplantation site, the nose catheter shaft 704 is moved distallyrelative to the balloon catheter shaft 20 (in the direction of arrow712) to uncover the valve 12 and the balloon 28 for subsequentdeployment of the valve. Desirably, although not necessarily, the nosepiece 702 can be partially inflated so that it can more readily assumethe inverted position shown in FIG. 24A. In this regard, the lumen ofthe nose catheter shaft 704 can be fluidly connected to a fluid sourcefor partially inflating the nose piece 702, similar to the way theballoon catheter shaft is used to deliver a fluid to the balloon 28.

FIG. 25A shows the distal end portion of a modification of the deliveryapparatus 10. The delivery apparatus in this embodiment includes astepped balloon 800 mounted on the distal end portion of the ballooncatheter shaft 26 and inner shaft 34. As shown in FIG. 25B, theillustrated balloon 800 includes a first slender portion 802, a firstconical portion 804, a main cylindrical portion 806, a second conicalportion 808, a second cylindrical portion 810, a third conical portion812, and a second slender portion 814. A valve 12 (FIG. 25A) can bemounted in a crimped state on the main cylindrical portion 806. Thestepped balloon 800 is further described in detail in co-pending U.S.application Ser. No. 11/252,657 (the '657 application) (published asU.S. Patent Application Publication No. 2007/0088431), which isincorporated herein by reference.

As shown in FIG. 25A, the delivery apparatus includes a guide cathetercomprising a guide catheter shaft 22 having an enlarged end portion 816that abuts the proximal end of the valve 12. The guide catheter furtherincludes a retractable cover 818 that extends over and covers the valve12. The cover 818 is operable to slide longitudinally relative to thevalve and the distal end of the guide catheter shaft 22 to uncover thevalve for deployment inside a body vessel. Portions 802, 804 of theballoon 800 extend from the distal end of the cover 818 and can bepartially inflated to provide a transition member between the distal endof the balloon catheter and the cover 818, thereby facilitating trackingthrough the patient's vasculature, much like nose piece 32 (FIG. 1). Theend of the balloon extending from the cover 818 also can be used as adilator to dilate stenotic leaflets of a native heart valve or otherportions of the patient's vasculature prior to deploying the valve atthe desired implantation site, as further described in the '657application.

As further shown in FIG. 25A, the cover 818 in the illustratedembodiment has a cylindrical distal end portion 820 that extends overthe valve 12 and a plurality of circumferentially spaced fingers 822extending proximally from the proximal end of the cylindrical distal endportion 820. The proximal end portion of each finger 822 is connected toa pull wire 826 that extends through a respective lumen in the guidecatheter shaft 22. As shown in FIG. 25C, each pull wire 826 extendsdistally from a respective lumen 828, through an opening 830 in theproximal end portion 824 of a respective finger 822, and back into thelumen 828. The guide catheter can further include a flexible outer cover838 extending over the portions of the pull wires 826 extending from theshaft 22 to prevent the wires from contacting the inner walls of thevasculature. The cover 838 can be fixedly secured to the outer surfaceof the shaft 22, such as with a suitable adhesive. Alternatively, thecover 838 can be adapted to slide longitudinally relative to the shaft22.

The cover 818 in the illustrated example has four fingers 822, each ofwhich is connected to a pull wire 826 that extends through a respectivelumen 828. As shown in FIG. 25D, the lumens 828 can be equally spacedaround a central lumen 54 of the shaft 22. The shaft 22 also can includeanother lumen for receiving a pull wire 74 for adjusting the curvatureof the guide catheter, as described above. The pull wires 826 extend thelength of the guide catheter shaft 22 and are operatively connected toan adjustment mechanism at the proximal end of the shaft to permitmanual adjustment of the pull wires 826, and therefore the cover 818.

FIG. 25E is a schematic illustration of a handle portion 832 connectedto the proximal end of the guide catheter shaft. The handle portion 832can have a construction similar to the handle portion 20 (describedabove and shown in FIGS. 3A-3B) except that the former can include anadditional adjustment mechanism 834 connected to the pull wires 826. Theadjustment mechanism 834 can be moved fore and aft (in the directions ofdouble-headed arrow 836) by the operator to move the pull wires 826. Thepull wires 826 desirably exhibit sufficient rigidity to apply a pushingforce to the cover 818 in the distal direction without buckling. Thepull wires can be, for example, 0.006 inch×0.012 inch Nitinol ribbonwire. In this manner, the cover 818 can be retracted in the proximaldirection relative to the valve, and if necessary, moved in the distaldirection, such as to retrieve the valve back into the cover 818, byoperation of the adjustment mechanism 834. Further details of anadjustment mechanism that can be used to produce movement of the pullwires in the distal and proximal directions is described in detail inthe '657 application.

When the valve is advanced to the implantation site inside the body, thecover 818 is retracted by operation of the adjustment mechanism touncover the valve. As the cover 818 is retracted (relative to the shaft22 and the outer cover 838), the distal end of the shaft end portion 816abuts against the valve to prevent inadvertent movement of valve'sposition on the balloon 800. Thereafter, the balloon catheter can beadvanced distally relative to the guide catheter to advance the balloon800 a sufficient distance from the cover 838 and the shaft end portion816 to permit full inflation of the balloon for deploying the valve 12.The valve 12 can be a balloon-expandable valve that is deployed by theballoon, or alternatively, the valve 12 can be a self-expanding valvethat radially expands when advanced from the cover 818. In the lattercase, the balloon 800 can be used to further expand the valve to ensuretight engagement with the orifice of the native valve.

In an alternative embodiment, the shaft distal end portion 816 can beconfigured to provide a releasable attachment to the valve 12, such asdescribed in detail in the '657 application. In this manner, the guidecatheter can be moved fore and aft to adjust the position of the valvein the body vessel as the valve is being deployed. Prior to deployment(or after partial deployment, or expansion, of the valve), control ofvalve positioning can be achieved by the operator pushing, pulling, ortwisting the guide catheter. Once the operator is satisfied with theposition of the valve, the valve can be fully deployed and the valve isdetached from the distal end of the guide catheter shaft.

FIGS. 25A-25E illustrate another embodiment of an introducer sheath,indicated at 900, that can be used to facilitate the introduction of adelivery apparatus into a blood vessel. The introducer sheath 900 has anexpandable, elongated sleeve 902 that can be radially expanded from afirst diameter (FIG. 25A) to a second, larger diameter (FIG. 25B) tofacilitate insertion of the largest portion the delivery apparatus (theportion on which the valve or other prosthetic device is mounted). Thesheath 900 further includes a handle portion 904 connected to theproximal end of the sleeve 902. The sleeve 902 includes an inner layer906 and an outer layer 908. The inner layer 906 can be a braidedpolymeric layer made from a suitable material such as, peek, nylon, orpolypropylene. The outer layer 908 can be formed from urethane oranother suitable material. The outer surface of the outer layer 908 canbe provided with a hydrophilic coating. The handle portion 904 can houseone or more sealing valves configured to sealingly engage the outersurface of a delivery apparatus inserted through the sheath, aspreviously described.

As shown in FIG. 25C, the sleeve 902 can be formed with a main lumen 910sized to permit passage of a delivery apparatus and one or more innerconduits 912 defining side lumens spaced around the main lumen 910.Extending through each side lumen is a respective pull wire 914. Theproximal end of each pull wire 914 is connected to an adjustmentmechanism 916 on the handle portion 904. The distal end of each pullwire 914 is fixedly secured to the distal end portion of the sleeve 902.For example, as shown in FIG. 25D, each pull wire 914 can extendoutwardly from the distal end of a respective lumen and can be welded tothe inner layer 906 adjacent the distal end of the sleeve.

The adjustment mechanism 916 is configured to permit manual adjustmentof the diameter of the sleeve 902 between a first diameter (FIG. 25A)and a second, larger diameter (FIG. 25B). In the illustrated embodiment,for example, the adjustment mechanism can move longitudinally relativeto the handle portion 904, in the directions indicated by double-headedarrow 918. Moving the adjustment mechanism in the proximal direction(away from the sleeve 902) is effective to pull the pull wires 914 inthe same direction, which causes the sleeve 902 to radially expand andto shorten in length. Moving the adjustment mechanism 914 in the distaldirection (toward the sleeve) releases tension on the pull wires 914 topermit the sleeve 902 to radially contract and elongate under its ownresiliency. In particular embodiments, the sleeve 902 has an outerdiameter of about 18 F in its contracted state and can expand to anouter diameter of about 28 F.

In use, the sleeve 902 can be inserted into a blood vessel as previouslydescribed. As a delivery apparatus (e.g., delivery apparatus 10) isinserted through the sleeve 902, the sleeve 902 can be radially expandedto allow a prosthetic valve (e.g., valve 12) or other prosthetic devicemounted on the delivery apparatus to easily pass through the sleeve 902.Once the prosthetic valve is inserted into the blood vessel, the sleeve902 can be reduced in diameter to minimize occlusion of the vessel.

In an alternative embodiment, as depicted in FIG. 25E, the inner layer906 can be a laser cut tube rather than a braided layer. The tube can beformed with a plurality of longitudinally extending cuts or slits 920that allow the tube to radially expand and contract.

The various embodiments of the delivery apparatus disclosed herein canbe used for implanting prosthetic devices other than prosthetic heartvalves into the body. For example, the delivery apparatus can be used todeliver and deploy various types of intraluminal devices (e.g., stents,stented grafts, etc.) into many types of vascular and non-vascular bodylumens (e.g., veins, arteries, esophagus, ducts of the biliary tree,intestine, urethra, fallopian tube, other endocrine or exocrine ducts,etc.). In one specific example, the delivery apparatus can be used toimplant a balloon-expandable stent into a coronary artery (or otherblood vessels) to maintain the patency of the vessel lumen.

In view of the many possible embodiments to which the principles of thedisclosed invention may be applied, it should be recognized that theillustrated embodiments are only preferred examples of the invention andshould not be taken as limiting the scope of the invention. Rather, thescope of the invention is defined by the following claims. We thereforeclaim as our invention all that comes within the scope and spirit ofthese claims.

We claim:
 1. A delivery apparatus, comprising: a handle; a first shaftextending from the handle; a second shaft disposed around the firstshaft; and a valve cover coupled to a distal end portion of the firstshaft and configured to house a prosthetic heart valve in a radiallycompressed state, wherein the valve cover has an outer diameter greaterthan an outer diameter of the second shaft, and wherein the first shaftand the valve cover are movable together in an axial direction relativeto the second shaft.
 2. The delivery apparatus of claim 1, incombination with a radially expandable and compressible prosthetic heartvalve disposed within the valve cover in a radially compressed state. 3.The delivery apparatus of claim 2 in combination with the prostheticheart valve, wherein the first shaft and the valve cover are movabletogether relative to the second shaft to uncover the prosthetic heartvalve.
 4. The delivery apparatus of claim 3 in combination with theprosthetic heart valve, further comprising an inflatable balloondisposed on the distal end portion of the first shaft beneath theprosthetic heart valve, wherein the balloon is inflatable from adeflated configuration to an inflated configuration, thereby radiallyexpanding the prosthetic heart valve from the radially compressed stateto a radially expanded state.
 5. The delivery apparatus of claim 3 incombination with the prosthetic heart valve, wherein the prostheticheart valve is a self-expanding prosthetic heart valve that radiallyexpands when advanced from the valve cover.
 6. The delivery apparatus ofclaim 5 in combination with the prosthetic heart valve, wherein thedelivery apparatus comprises a pusher to assist in advancing theprosthetic heart valve from the valve cover.
 7. The delivery apparatusof claim 1, wherein the second shaft comprises a steerable portionhaving an adjustable curvature.
 8. The delivery apparatus of claim 7,further comprising an adjustment mechanism coupled to the steerableportion and configured to adjust a curvature of the steerable portion.9. The delivery apparatus of claim 7, wherein the second shaft includesone or more pull wires extending along a length of the second shaft andcoupling the steerable portion to an adjustment mechanism in the handle.10. The delivery apparatus of claim 1, wherein the first shaft definesan inner lumen through which a guide wire extends.
 11. The deliveryapparatus of claim 1, wherein an inner diameter of the second shaft issmaller than the outer diameter of the valve cover.
 12. A medicalassembly for replacing a native heart valve, comprising: a deliveryapparatus comprising: a handle, a first shaft extending from the handle,a second shaft disposed around the first shaft, and a valve covercoupled to a distal end portion of the first shaft and having an outerdiameter greater than an outer diameter of the second shaft, wherein thefirst shaft and the valve cover are movable together in an axialdirection relative to the second shaft; and a prosthetic heart valvemounted in a radially compressed state within the valve cover fordelivery through a patient's vasculature, the prosthetic heart valvecomprising a radially compressible and expandable stent and a flexiblevalve structure mounted within the stent.
 13. The medical assembly ofclaim 12, wherein the prosthetic heart valve is a self-expandingprosthetic heart valve that radially expands when advanced from thevalve cover.
 14. The medical assembly of claim 13, wherein the firstshaft and the valve cover are movable relative to the second shaft toadvance the prosthetic heart valve from the valve cover.
 15. The medicalassembly of claim 12, wherein the second shaft comprises a steerableportion having an adjustable curvature.
 16. The medical assembly ofclaim 12, wherein an inner diameter of the second shaft is smaller thanthe outer diameter of the valve cover.
 17. The medical assembly of claim12, wherein the second shaft has a free distal end.
 18. A method,comprising: inserting a distal end portion of a delivery apparatus intothe vasculature of a patient, the delivery apparatus releasably coupledto a prosthetic heart valve, the delivery apparatus comprising: ahandle, a first shaft extending from the handle, a second shaft disposedaround the first shaft, and a valve cover coupled to a distal endportion of the first shaft and housing the prosthetic heart valve in aradially compressed state, the valve cover having an outer diametergreater than an outer diameter of the second shaft, wherein the firstshaft and the valve cover are movable together in an axial directionrelative to the second shaft; and advancing the prosthetic valve to aselected implantation site; moving the first shaft and valve coverrelative to the second shaft to expose the radially compressedprosthetic heart valve; and expanding the prosthetic heart valve fromthe radially compressed state to a radially expanded state.
 19. Themethod of claim 18, wherein the prosthetic heart valve self expands fromthe radially compressed state to the radially expanded state whenexposed from the valve cover.
 20. The method of claim 18, wherein aninner diameter of the second shaft is smaller than the outer diameter ofthe valve cover.